The invention relates to instruments and techniques for measuring the total amount of gas dissolved in a liquid, solvent or solution and more particularly to a new and improved apparatus for measuring total dissolved gas pressure in fluids.
The determination of total, as contrasted to individual or partial, gas pressures provides valuable information as to the degree to which equilibrium with the gaseous environment or the atmosphere has been established. For the purposes of this discussion and description, total dissolved gas pressure in a liquid means the sum total of all partial pressures of all gases dissolved in the liquid including the vapor pressure of the liquid. Total gas pressure information is also valuable in studies to determine relationships between excess pressures and environmental conditions which have created supersaturation problems. As mentioned above, fish and aquatic life in rivers, lakes, hatcheries, aquaria and other aquaculture projects have often died of gas embolism because of the excess total pressure of dissolved gases in these various bodies of water. Such a condition facilitates bubble formation in the organisms with fatal results. As a result, instruments capable of quickly and easily providing the dissolved gas pressure information are currently used and increasingly needed both to study the condition of "gas bubble disease" and to monitor waters where there is any likelihood of danger or risk to fish and aquatic life.
As those skilled in the art are aware, water in which there is as little as 10% or perhaps even less excess of dissolved gas can be lethal to fish life. Any pumped or otherwise pressurized water supply can present a risk and hence it is necessary to know the levels of air or dissolved gases in a particular system. In addition, many industries aerate or sparge water or other fluids with air or other gases to saturate with or remove air or other gases. Measuring techniques such as that herein described facilitate economical quality control where used.
Instruments and techniques for measuring total dissolved gas and fluid vapor pressures in solutions have for the most part been concerned with particular gaseous components as opposed to measuring the total pressure of all gases dissolved in the fluid. Some of the more obvious applications of a device for measuring total dissolved gases are in the area of water pollution, industrial and other waste water analysis, fish hatchery water quality, aquarium water quality, wine, beer and beverage production and any other application where it is desired to assess the state of gas pressure equilibrium or disequilibrium between the water or fluid and a gas phase. Accordingly, the invention's recent application to water quality and atmospheric saturation is an obvious example of general applications requiring knowledge of the saturation state of any liquid with any gas phase, although an external gas phase per se is not necessary for the measurement. Clearly, these more general uses include numerous industrial and even space applications, and provide a new analytical method of greater convenience and simplicity.
Current state-of-the-art instrumentation is unnecessarily cumbersome and expensive. Some of the prior instruments, sometimes referred to as "saturometers" or "gasometers", require time consuming and tedious procedures, sometimes require water pumps and as a result present prohibitive disadvantages if a large number of measurements must be taken to monitor a relatively large body of water, or if remote measurements at depth must be made. Additionally, known "saturometers" and "gasometers" and their use require skill and training in the operators, are very susceptible to damage and do not provide an absolute pressure reading but a gauge pressure which due to barometic pressure fluctuations is subject to error. Also, the use of dial gauges employing a Bourdon tube imposes further equilibration time requirements and gradual gauge errors due to corrosion; further the use of mercury in an open-ended manometer increases the size of the devices using it. Additionally, such devices all require an operator or observer at the measuring site which increases the cost of measurements and decreases the utility of the devices. The above are among the more apparent disadvantages of present equipment and devices.
Among the known prior art publications relating to this subject matter are the following United States Letters Patent.
U.S. Pat. No. 3,438,241 is a structurally unrelated device which is directed toward selected gas pressure measurement as opposed to total dissolved gas pressure.
U.S. Pat. No. 3,871,228 is directed to a device for total pressure measurement but structurally and functionally is significantly different from that of the instant application.
U.S. Pat. No. 4,366,700 also measures total dissolved gas dissolved in a fluid but again is also structurally significantly different from the instant device.
U.S. Pat. Nos. 3,668,837 and 3,673,864 are of interest only and significantly unrelated to the specifics of the instant invention.